Osteopenia is common in Turner's syndrome. Despite the proven association between EE[2] deficiency and osteoporosis, EE[2] treatment in Turner's syndrome does not normalize bone mineral content. Using stable isotopes of calcium (Ca) we determined Ca fractional absorption, balance, and bone deposition in 7 children (10-16 y old) and 4 adults (16-34 y old) with Turner's syndrome. Each subject was studied before and after 3 months of GH treatment (0.1 mg/kg/d in adults and 0.05 mg/kg/d in children). All adults were treated with EE[2] (50 microgram/d) and progesterone before and throughout the study. Three children received no EE[2] and 4 children were treated with low dose (5 microgram/d) EE[2] in combination with GH. GH did not affect Ca kinetics in adults already taking a regime of EE[2]/progesterone replacement. GH alone also did not affect calcium kinetics in children. However, addition of EE[2] to GH treatment in children resulted in a significant increase in Ca absorption, Ca balance and Ca turnover. Although this study did not examine isolated effects of EE[2] on Ca kinetics, we conclude that GH alone neither stimulates bone deposition nor influences Ca kinetics in children or adults with Turner's syndrome. However, addition of low dose estrogen to a regimen of GH may improve bone deposition and calcium balance in girls with Turner's syndrome.